Electrodeposition of nickel from an acid bath



Patented Sept. 19, 1950 ELECTRODEPOSITION OF NICKEL FROM AN ACID BATH Hem-y Brown, Detroit, Mich assignor to The Udylite Corporation, Detroit, Mich, a corporation 01' Delaware No Drawing. Application July 7, 1945, Serial No. 603,753

2 Claims.

This invention relates to the electrodepositlon of'nickel from aqueous acidic nickel baths.

The object of this invention is to decrease the grain size and increase the luster and brightncss of the nickel deposit without decreasing appreciably the ductility of the plate or the current density range of the nickel bath.

This object can be accomplished by the addition or certain unsaturated aliphatic sulfonic acids such as the alpha and/or beta unsaturated aliphatic sulfonic acids as exemplified by vinyl sulfonic acid (CH2=CHSO3H) and allyl sulionic acid (CH2=CHCH2SO3H). In Table I are listed a number of alpha and beta unsaturated aliphatic sulfonic acids and their optimum concentrations in the nickel baths. Actually they all can be used up to saturation in the baths, that is, they do not have critical upper concentration limits.

Th brighteners listed in Table I can be used in any type of operating acidic nickel baths with beneficial effects. In Table II are listed by way of illustration a number of such acidic nickel baths.

The nickel plate obtained with the alpha and beta unsaturated sulfonic acids present in the acidic baths is very fine-grained, of good color and ductile, and remarkably free from pitting. On bufied surfaces the plate obtained is as good in reflectivity and brightness as the base.

It is a surprising and remarkable fact, for example, that in a warm nickel chloride bath (Bath No. 2-300 g./l.NiCl2.6H2O and 35 g./l.H3BOa) which gives very brittle darkish plate (evidently due to basic salt inclusions) at pH values of 4-5, the addition of about 8 g./l. of vinyl sulfonic or allyl sulfonic acid (added as the Ni salt) will produce very ductile fine-grained plate of good luster or brightness and color under otherwise the same conditions, i. e., temperatures, pH values, and current densities whereas 1,5 naphthalene disulfonic acid will not accomplish this, and the plate is still very brittle and of poor color (it is, however, finer grained than the plain nickel chloride bath). These facts also hold true in other high speed plating baths containing high nickel chloride concentrations, for example, 150 g./l. of nickel sulfate and 150 g./l. of nickel chloride. It is also interesting to note that formaldehyde alone at about 1 g./l. also gives brittle,

2 darkish, fine-grained. frosty plate in the high nickel chloride baths.

If. other nickel brighteners such as, for example, zinc or cadmium in a concentration of about 0.1-0.5 g./l. are present in acidic nickel baths besides a sufilcient concentration 01'' a compound (or compounds) of Table I, the plate obtained is brighter than with either material alone in the bath. Also, the bath can tolerate larger concentrations of the zinc and cadmium than the plain bath without getting brittle, darkish, poorly adherent plate. This is also true with respect to thallous and mercuric salts in about the same concentrations. It is also true with respect to the impurity, copper, which does not produce any appreciable brightness when present in small concentrations, but tends, instead to very readily produce dark deposits, first appearing at the lowest current densities and extending upward as the concentration or copper is increased. In fact with respect to increasing the tolerance of the nickel bath to such materials which plate out preferentially to the nickel and tend at the slightest excess to discolor the very low current areas, the vinyl and allyl sulfonic acids ar extremely good. That is, they are very effective for the very low current density values while at the same time being very efiective for the middle and high current density values.

While the beta unsaturated aliphatic sulfonic acids (e. g., allyl sulfonic acid) are similar in their efl'ects in the nickel baths to the alpha unsaturated sulfonic acids (e. g., vinyl sulfonic acid) they differ to a certain degree. The vinyl sulionic acid, for example, makes possibl a toleration of somewhat larger concentrations of materials (both inorganic and organic) which plate out preferentially to nickel and which when alone in the bath cause brittle and easily stained plate of poor color. Apparently, the beta olefinic double bond as present in allyl sulfonic acid does exert an eilect on, or transmits an eilect to, the sulfonic group and increases its reactivity, but not as strongly as does an alpha unsaturated bond. Apparently, conversely the sulfonic group affects the active unsaturation characteristics of the alpha carbon double bonds more strongly than the more distant beta, that is, the beta double bonds are more strongly olefinic in character, and thus allyl sulfonic acid also exerts a brightening effect in a somewhat similar manner as does allyl alcohol, allyl amine, allyl urea, arsonic acid, and acrylic acid. The latter, however, do not increase the toleration of impurities,

in fact; they decrease the tolerance. For example, in the higlr'nickel chloride bath (e. g., Bath No. 2), the addition of sodium or nickel acrylate, from 1 g./l. to saturation only produces :[iner grain but the plate is still dark and very brittle. It is also interesting to note that saturated aliphatic sulfonic acids (when pure), unlike the alpha or beta unsaturated aliphatic sulfonic acids, do not produce brightness or such desirable efiects. I

to materials whicht of mercaptans or sulphites left over from some of the starting materials used in the synthesis. For example, pure ethane sulfonic acid or pure 2-bromo ethane sulfonic acid do not produce any appreciable brightening effect, nor do pure saturated aliphatic sult'ones such as Sulfonal."

The alpha and beta unsaturated sulfonic acids can be used with beneficial effects in other acidic nickel baths, besides those listed in Table II, for example, in baths made up with nickel sulfamate allyl the naphthalene sulfonic acids, the benzene sulfonic acids, the benzene sulfonamides, the diphenyl sulfone sulfonic acids, in that the ductility of the plate and the brightness in the recesses .(low current density areas) is improved. This is especially true'if-ithe chloride concentration of such nickel baths'is above '75 g./l. NiClaGHzO.

r TABLE 1' Alpha and beta unsaturated aliphatic sulfom'c acids H 7 Opt. Oonc. i '4"- (9/13 1.. on 891011(Ni,Co,Na,K,ol'Mgsalt) 1-8 '-:'(vin y1su1fonicacid) 2. cage-salon Ni, 00, Na, K, or Mg salt) 1-8 I Br v a. CHF-SOQOH (N1, 00, Na, K, or Mg salt) 1-8 H H 4. CH lCI I-SOzOH (Ni, 00, Na, K, or Mg salt) 1-8 (allyl sullonic acid) 01 Cl 5. cnpd-d-solon (Ni, 00, Na, K, or Mg salt) 1-6 H H a. Gino-sown (Ni, 00, Na, K, or Mgsalt) in whole or in part. 1-8

TABLE II Buffer Other Salts NlSOl NlClz Current Q? 11120, 6H2O, pH Density,

Formula g./l, Formula g./l. ampsJsq' H313 O; (boric acid)... 75-160 2-6 10-75 HaB O3 75-160 1-5 10-100 do 75-160 2-6 10-85 H. C 80 H (formic acld) 75-140 3-6 10-60 75-140 2-6 10-60 11% MgSOl.7HzO... 125 75-160 2-0 10-60 o Ni citrate 8 N801 40 75 5. 5 10-25 B11303 JJI$I $2 75 1H5 .d0 l5 NHlCl 75 5.3 5-20 The best bufler as far as the cathode film is concerned is boric acid and is preferred, though other bufi'ers can be, used, as, for example, formic, citric, or fluoboric acids.

Mixtures of compounds of Table I can be used with beneficial eifects (improved brightness of plate) as, for example, allyl sulfonic acid with vinyl sulfonic. Also mixtures of the compounds of Table I with aryl sulfonates, aryl sulfonamides, aryl sulfimides, aryl sulfone sulfonic acids enhance or improve the brightness of the plate. For example, 0.1-.2 g./l. of o-benzoyl sulfimide with 0.1- 3 g./l. of vinyl and allyl sulfonic acids. In general the nickel salts of the alpha or beta unsaturated aliphatic sulfonic acids are preferred for additions instead of the free acids in order not to alter the pH of the baths very much.

Even concentrations as low as 0.1 g./l. of compounds of Table I show beneficial efiects over small ranges of current density, though in general at least 1 g./l. concentrations should be used. The alpha and beta unsaturated'sulfonic acids such as the vinyl (ethylene) sulfonic acids and the allyl sultonic acids are very beneficial when added to acidic nickel baths containing from .1 g./l. to saturation Of any one or more of the following:

lustrousnickel consisting essentially of an aqueous acid solution of a material selected from the group consisting of nickel chloride, nickel sulfate, a mixture of nickel sulfate; and nickel chloride, a mixture of nickel fluoborate and nickel chloride, a mixture of nickel fluoborate and nickel sulfate, a mixture of nickel sulfate, nickel chloride and nickel fluoborate, said' solution also having dissolved therein an unsaturated organic compound selected, from the group consisting of vinyl sulfonic acidr(CI-I2':=CHSO:;H), chlor vinyl sulfonic acid andjbrom vinylsulfonic. acid, said unsaturated organic compound having a concentration in the bath falling within a range of from about 1 gram per liter to saturation.

2. A method for electrodepositing fine-grained, lustrous nickel comprising the step of electrodepositing fine-grained, lustrous nickel from an aqueous acid solution consisting essentially of a material selected from the group consisting of nickel chloride, nickel sulfate, a mixture of nickel sulfate and nickel chloride, a mixture of nickel REFERENCES CITED fiuoborate and nickel chloride, a mixture of nickel The following references are of record in the fiuoborate and nickel sulfate, a mixture of nickel me of this patent:

sulfate, nickel chloride and nickel fiuoborate, said solution also having dissolved therein an unsatu- 5 UNITED STATES PATENTS rated organic compound selected from the group Number Name Date consisting of vinyl sulfonic acid (CH2=CHSOBH) 1,818,229 Lutz Aug. 11, 1931 chlor vinyl sulfonic acid and brom vinyl sulfonic 2,029,387 Pine Feb. 4, 1936 acid, said unsaturated organic compound having 2,112,818 Waite Mar. 29, 1938 a concentration in the bath falling within 'a range 10 2,125 229 Harshaw 1; 1 July 26, 1933 of from about 1 gram per liter to saturation. 2,171,842 r ett 1; ,1 S t, 5, 1939 HENRY BROWN. 2,198,267 Lind 61; a1 Apr. 23, 1940 

1. A BATH FOR ELECTRODEPOSITING FINE-GRAINED, LUSTROUS NICKEL CONSISTING ESSENTIALLY OF AN AQUEOUS ACID SOLUTION OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF NICKEL CHLORIDE, NICKEL SULFATE, A MIXTURE OF NICKEL SULFATE AND NICKEL CHLORIDE, A MIXTURE OF NICKEL FLUOBORATE AND NICKEL CHLORIDE, A MIXTURE OF NICKEL FLUOBORATE AND NICKEL SULFATE, A MIXTURE OF NICKEL SULFATE, NICKEL CHLORIDE AND NICKEL FLUOBORATE, SAID SOLUTION ALSO HAVING DISSOLVED THEREIN AN UNSATURATED ORGANIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF VINYL SULFONIC ACID (CH2=CHSO3H), CHLOR VINYL SULFONIC ACID AND BROM VINYL SULFONIC ACID, SAID UNSATURATED ORGANIC COMPOUND HAVING A CONCENTRATION IN THE BATH FALLING WITHIN A RANGE OF FROM ABOUT 1 GRAM PER LITER TO SATURATION. 